According to researchers from UC Davis and Aarhus University in Denmark, the Earth's molten core may be leaking iron as heavier iron isotopes circulate back down into the core. This effect might cause core material infiltrating the lowermost mantle to be enriched in heavy iron isotopes.

Heavy iron isotopes are leaking

Below the Earth's surface the boundary between the liquid iron core and the rocky mantle is located some 1,800 miles or 2,900 kilometers. The temperature drops by more than a thousand degrees from the hotter core to the cooler mantle at this transition.

Isotopes although coming from the same element have different masses because they have different numbers of neutrons. In the study, those heavier iron isotopes transfer to the lower temperatures and into the mantle. Meanwhile iron isotopes with lighter weight circulate back down into the core.

This effect could result in the core material entering the mantle's lowermost part to be enriched in heavy iron isotopes.

Study lead author, professor emeritus of geology at UC Davis and Aarhus University's Earth system petrology professor, Charles Lesher, said that understanding the physical processes operating the core-mantle boundary is essential for understanding seismic images of the deep mantle.

Moreover, it is also essential to modeling the extent of chemical and thermal transfer between the deep Earth and surface of our planet.

As noted by Lesher, their analysis shows how iron isotopes move from between different temperatures when they conducted experiments under high temperature and pressure. It explains the anomaly found in lava emissions and eruptions.

This also explains why there are more iron isotopes in mantle rocks than in chondrite meteorites which are ancient materials during the formative years of the Solar System. He added that if this is true, the results suggest that the Earth could have been leaking iron isotopes into the mantle for billions of years already.

They published their research in Nature Geoscience on April 6.

Isotopes in volcanic island rocks

The researchers conducted computer simulations to show that the core material can even reach the Earth's surface through the hot, and upwelling mantle plumes. Lesher and his team propose that the lavas erupted at oceanic hot spots like the ones in Samoa and Hawaii are enriched in heavy iron isotopes which could be a sign of a leaky core.

In a separate study by an assistant professor at Carleton University in Ottawa, Hanika Rio and her colleagues describe evidence that Earth's core may be interacting and maybe exchanging material with the lower mantle.

Using the magma-derived rocks from volcanic islands above oceanic hotspots like the Réunion in the Indian Ocean, which many think that it is where the core-mantle boundary originates, their team were able to study these materials from the core getting into the mantle.

She and her team were able to detect mantle plumes to be the path of these samples to the earth's surface using the newly precise measurements of a chemical isotope tracer.

Rizo and her team published their study in the Geochemical Perspectives Letters.